Tag Archives: Hypothyroidism

Has subclinical hypothyroidism which is being treated with levothyroxine (?link to refractory hypertension)

Hypothyroidism:

Primary hypothyroidism is characterized by a high serum thyroid-stimulating hormone (TSH) concentration and a low serum free thyroxine (T4) concentration

Subclinical hypothyroidism is defined biochemically as a normal free T4 concentration in the presence of an elevated TSH concentration. Secondary (central) hypothyroidism is characterized by a low serum T4 concentration and a serum TSH concentration that is not appropriately elevated

Presence of high serum concentrations of abs to thyroid peroxidase (TPO) and thyroglobulin

Do not routinely measure TPO abs in patients with primary overt hypothyroidism because almost all have chronic autoimmune thyroiditis – can be measured in subclinical hypothyroidism to predict likelihood of progression to permanent overt hypothyroidism

Secondary hypothyroidism: <1 %

TSH deficiency

Pituitary necrosis (eg. Sheehan’s syndrome), trauma, pituitary tumors

Treat with Thyrotropin (TSH, Thyrogen). Usually also need to replace other pituitary hormones.

Treat with Protirelin (TRH, Relefact TRH). Usually also need to replace other pituitary hormones.

In hypothyroidism caused by hypothalamic or pituitary disease, TSH secretion does not increase appropriately as T4 secretion falls. As a result, the symptoms and the serum free T4 value must be used to make the diagnosis. Thus, we measure both serum TSH and free T4 if pituitary or hypothalamic disease is suspected (eg, a young woman with amenorrhea and fatigue)

The clearance of many drugs, including antiepileptic, anticoagulant, hypnotic and opioid drugs, is decreased in hypothyroidism. Thus, drug toxicity may occur if drug dose is not reduced. In addition, drugs that are administered at effective doses in patients who are hypothyroid may become less effective during T4 replacement.

data linking subclinical hypothyroidism with atherosclerosis and myocardial infarction and the increased risk of progression to overt hypothyroidism

supported by ATA, AACE, European thyroid association guidelines

TSH 7-9.9 mU/L: treat most under age 65-70 yo d/t association of increased CV mortality in younger patients. ?benefit in older patients and concerns of safety in older pts (↑ risk of exacerbation and induction of angina and CAD)

TSH ULN-6.9mU/L: treat <65 to 70 who have sxs suggestive of hypothyroidism. Consider if high titers of anti-TPO abs, and patients with goiter. For older patients, these levels of TSH may be age-appropriate.